5. Interface Temperature of Sliding Surfaces

The interface temperature between sliding surfaces plays an important role in the tribological performance of the surfaces. Temperature rise at the tribo-contacts can cause microstructural changes and tribo-chemical reactions, which in turn influence the operating wear mechanisms and wear transitions. Flash temperatures that arise at the tip of asperities are much higher than the surface bulk temperatures. Exact estimation of flash temperatures is rather difficult when compared to the surface bulk temperatures. However, calculations of surface bulk temperatures using models that are based on ab initio estimations, at the most, give values that are only indicative but not exact. The parametric uncertainties in these models give rise to either underestimates or overestimates of surface bulk temperatures. Estimation of surface bulk temperatures based on measurements can give temperature values closer to the real ones. This chapter presented a brief historical background on the subject of estimation of temperatures, earlier models based on ab initio calculations, and a new method to estimate surface bulk temperatures based on measurement of temperature at two points along a pin axis away from the sliding interface and in a realistic flow field of air around the pin. Discussion on the issues in the earlier models and comparison of temperature values obtained by these models with those estimated by measurements clearly indicate the importance of undertaking measurements to arrive at better estimates of temperature values that are closer to the real ones.